Due to ever increasing economic costs and shortages of fossil fuel sources, it has become desirable to develop alternative fuel sources. Commitment to energy and environmental conservation has also contributed to the drive to develop alternative fuel sources. Contemporaneously with this trend toward the development of alternative fuel sources, environmental and legal concerns and regulatory agencies have escalated the costs related to the disposal of industrial refuse and other wastes. Such escalation in cost has resulted in the development of alternative methods of refuse and waste disposal.
In response to these concerns, technical interest in the fuel value of urban solid refuse developed in Europe in the 1950's and spread to the United States in the late 1960's. Much of the work on refuse derived fuel to date has concentrated on urban solid refuse due to its enormous volume. The literature reports test in which pellets were produced by extrusion of urban solid refuse through a die using bench scale and commercial equipment and reports a relationship between power consumption and other process variables. Prezek, G. J., "Fundamental Considerations In Preparing Densified Refuse Derived Fuel", U.S. EPA, EPA/600/2-81-180, September, 1981. The literature further describes a test burn of 285 tons of urban solid refuse derived pellets mixed with coal in a spreader stoker fired boiler conducted at the Maryland State Correctional Institute in 1976 and 1977, and reports that coal:refuse derived fuel blends up to volumetric ratios of 1:2 can be burned without major equipment modifications. Dengler, G. H, Rigo, H and Riler, Jr., D. "A Field Test Using Coal: dRDF Blends in Spreader Stoker Fired Boilers", U.S. EPA, EPA 600-2/80-095, August 1980. The literature also reports a 1700 ton test burn of urban solid refuse derived pellets in an industrial spreader stoker boiler conducted in 1979 in which extensive data was collected on all aspects of the combustion process. Klinbens, N., "Coal: dRDF Demonstration Test On An Industrial Spreader Stoker Boiler", U.S. EPA, EPA-600/2-81-83, Volume 1, EPA-600/2 81-84, Volume 2.
Fly ash, a byproduct of coal combustion, is a solid refuse material generated by many boilers and other heat and power generating facilities in operation today. Typically, the fly ash is disposed in landfills, but due to both the escalation in the costs related to the transportation of fly ash to a landfill and the limited number of new landfills being approved by governmental and regulatory agencies, an alternative disposal method for fly ash has become desirable.
Until the advent of the present invention, it was not thought to be possible to successfully incorporate fly ash into a refuse derived fuel due to the inherent physical characteristics of fly ash. Supportive of this belief is the recognition that none of the refuse derived fuels reported in the above literature mentioned or suggested the possible incorporation of fly ash. It has now suprisingly and unexpectedly been found that a refuse derived fuel containing fly ash can be successfully produced and that such a refuse derived fuel exhibits not only good physical properties but also good heating values.